Core material for piping

ABSTRACT

A core material for piping comprising a cord portion and a belt portion which are integrally molded from a synthetic resin material and further having a hook portion integrally formed on one surface of at least any one of the cord portion and the belt portion, the core material for piping being provided to a required position of a facing sheet material, wherein hardness of the hook portion is set higher than the hardness of the cord portion and the belt portion, thereby having a required engagement strength while securing easiness of bending of the cord portion and the belt portion.

BACKGROUND OF THE INVENTON

1. Field of the Invention

The present invention relates to a core material for piping including a cord portion and a belt portion which are molded by a synthetic resin material, and having a hook portion integrally formed on a single face of at least any one of the cord portion and the belt portion, the core material for piping being provided on an edge portion at a required location of a facing sheet material of a seat and the like.

2. Description of the Related Art

Conventionally, a core material for piping has been provided on the inner face of a facing sheet material at a ridge portion of an automobile passenger seat, and sofa and chair etc. for office and home to provide their seat cushion with a feeling of luxury. As this core material for piping, strings having a high stiffness obtained from fiber materials were used before. In recent years, a core material for piping made of synthetic resin has been often used instead of the strings. This core material for piping made of synthetic resin has a cord portion composed of a long linear material and having a circular section, and a belt portion having a rectangular section and integrally molded along the longitudinal direction of the cord portion at the same time when the cord portion is formed.

The core material for piping made of synthetic resin having such a structure is attached to a ridge portion of a passenger seat or the like as follows. That is, first and second facing sheets are overlapped through their surfaces at the side edge portions on the sewed side, and a core material for piping is placed on the rear face side of the side edge portion of the second facing sheet material. The first and second facing sheet materials and the belt portion of the core material for piping are sewed along a boundary between the cording portion and the belt portion such that they are overlapped. The second facing sheet material is folded back so as to embrace the cord portion of the core material for piping, thereby forming a step portion between the first and second facing sheet materials. An ordinary seat cover is made in a relatively smaller size than the external dimension of the cushion so that no wrinkle or looseness appears in a sheet pad. For this reason, when the seat pad is covered with the seat cover, the cord portion of the core material for piping is raised from the surface of the first facing sheet material and separated because a pulling force acts on the sewed portion due to the repulsive force of the pad material. As a consequence, the step portion of the seat cover often meanders in an unstable fashion. Further, when a pressure by sitting of a person is applied, this tendency becomes more conceivable, so that the sewed portion between the core material for piping and the first and second facing sheet materials is exposed, thereby deteriorating the quality of sheet appearance.

In order to eliminate such inconvenience, for example, Japanese Patent Laid-Open Publication No. 2005-40158 discloses the following configuration. A core material for piping is placed on a side edge portion of overlapped first and second facing sheet materials along a side edge portion on the rear surface side of the second facing sheet material. Then, a belt portion of the core material for piping and the overlapped portion of the first and second facing sheet materials are sewed along a first sewing line, and the first and second facing sheet materials are sewed along a second sewing line near an end portion of the cord portion on an opposite side to the belt portion. Sewing along the second sewing line makes it possible to prevent the cord portion of the core material for piping from being raised from the surface of the first facing sheet material. According to Japanese Patent Laid-Open Publication No. 2005-40158, a plurality of hook pieces are provided on a single face of the core material for piping made of synthetic resin, and the hook pieces formed on the core material for piping are engaged with the rear surface of a folded portion of the second facing sheet material, thereby preventing the folded portion of the second facing sheet material from being raised.

By the way, a ridge portion of an automobile passenger seat and the like is not limited to a linear shape but often has a curved shape so as to be twisted in the longitudinal direction. Therefore, even if the seat cover is tried to cover the core material for piping so as to conform to the curved ridge portion of the seat pad after the core material for piping is provided along the curved edge portion of the facing sheet material, even if the seat cover is curved by twisting along the curved ridge portion of the seat pad and the like in case the core material for piping is stiff, the core material for piping tries to restore to its original linear state so that the seat cover cannot be conformed to the ridge portion of the seat pad.

Japanese Patent Laid-Open Publication No. 2005-40158 has described use of synthetic resin such as polypropylene as the molding material of the core material for piping. As the synthetic resin materials applied to the core material for piping include polyamide and polyester as well as polypropylene. However, the hardness of these synthetic resin materials is 100 or more in terms of Rockwell hardness, which is higher than the Rockwell hardness of polypropylene of 90 to 100 mentioned in Japanese Patent Laid-Open Publication No. 2005-40158. Even polypropylene having a relatively lower hardness than other thermoplastic resin materials, is considerably hard and lacks of plasticity. Therefore, if such a synthetic resin material is used, the cord portion often cannot be fitted well along the shape of the seat pad when the seat cover covers the seat cushion or the like. Thus, further devices are required to place the cord portion well along a complicated external shape of the seat pad.

As described in Japanese Patent Laid-Open Publication No. 2005-40158, when the hook pieces are formed on the surface of the belt portion of the core material for piping and the hook pieces are engaged with the back surface of the folded back portion of the second facing sheet material of a cushion cover, high pressure by sitting is applied to the passenger seat and the like, and at the same time, stress is applied from plural directions. For this reason, the engagement strength between the hook pieces and the back surface of the second facing sheet material needs to be increased. However, the engagement strength of the hook pieces is largely affected by the configuration and hardness of the hook pieces themselves and the structure of the engaging/disengaging face of the back surface of the mating second facing sheet material. Usually, the facing sheet material is obtained by laminating and integrating a facing layer composed of woven/knitted fabric, hide or synthetic leather, a cushion layer composed of a thin urethane material, and a back base cloth composed of knit goods or unwoven fabric, respectively by lamination processing and the like.

Therefore, the back surface of the facing sheet material is different from a female engaging member in which piles are gathered densely, each having an appropriate shape facilitating engagement with a hook piece used in an ordinary surface fastener. Often, the height of the pile is not sufficient, and the pile configuration is not uniform. For this reason, a hook piece having an ordinary hook piece structure and hardness is difficult to engage with the back surface of the facing sheet material securely. Even if the engagement is made, the percentage of the number of engaging hook pieces is small. Therefore, the entire engagement strength is low, so that the hook piece is easy to loose out if a strong force is applied. Thus, the hardness of the hook piece needs to be set higher than the hardness of an ordinary hook piece. However, if the hardness is too high, the engagement strength can be intensified, but the cord portion and the belt portion composed of the same material become difficult to bend, thereby causing the above-described faults.

The present invention has been achieved to meet such conflicting demands of easiness of curving of a core material for piping and likeliness of engagement of a hook portion. Specifically, an object of the invention is to provide a core material for piping made of synthetic resin, in which easiness of bending of the cord portion and the belt portion is secured, and the hook portion is provided with required engagement strength.

SUMMARY OF THE INVENTION

The above-described object is achieved effectively by a core material for piping comprising a cord portion and a belt portion which are molded from a synthetic resin material and having a hook portion integrally formed on one surface of at least any one of the cord portion and the belt portion, the core material for piping being provided to a required position of a facing sheet material of, such as a seat, being characterized in that hardness of the hook portion is set higher than the hardness of the cord portion and the belt portion.

The hardness of the hook portion is set to a required hardness which can secure a necessary engagement strength, and further, the hardness of the cord portion and the belt portion of the core material for piping is set to a lower hardness than that of the hook portion which allows them to be bent easily along the external shape of the cushion material. Consequently, the core material for piping sewed to the seat cover can be covered easily and securely along the external shape of the ridge portion of the seat pad. In addition, engagement of the hook pieces with the back surface of the second facing sheet material at the folded portion of the second facing sheet material, which is folded back to embrace the core material for piping inside, is carried out securely and strongly.

Preferably, the cord portion and the belt portion are composed of elastomer resin, and the hook portion is composed of thermoplastic resin. Further preferably, the hook portion is provided continuously or intermittently on entire one surface of at least any one of the cord portion and the belt portion. The hook portion may be constituted of a plurality of hook pieces only, and the respective hook pieces are erected directly from one surface of at least any one of the cord portion and the belt portion. More preferably, a surface of the core material for piping on which hook pieces are formed is a flat plane. The sewing area of the core material for piping may be formed more plastic than other portions, and the hook pieces may be excluded from the sewing area of the hook portion, on which the facing sheet material is to be sewed. In addition, the belt portion may be so constructed that the portion on an opposite side to the cord portion is cut out in a zigzag fashion instead of being formed in an ordinary long rectangular plane plate.

If the cord portion and the belt portion are composed of elastomer resin and the hook portion is composed of thermoplastic resin, the hardness of the hook portion can be set higher than the hardness of the cord portion and belt portion materially. Further, if the surface of the hook portion on which the hook pieces are formed is a flat plane, the height of the hook can be made common, so that the engagement strength in the hook piece formation area can be equalized. By providing the hook portion continuously or intermittently on the entire one surface of at least any one of the cord portion and the belt portion, the engagement strength of the hook pieces, and easiness of bending of the cord portion and the belt portion can be adjusted. If one side of the belt portion of the core material for piping is cut out in a zigzag shape, the core material for piping itself becomes easier to be bent. If the hook pieces are excluded from the sewing area of the hook portion in which the facing sheet is to be sewed, sewing operation with a sewing machine is facilitated, which is preferable. Moreover, if the sewing area is formed more plastically than the other portions by erecting respective hook pieces on one surface of at least any one of the cord portion and the belt portion or excluding the hook portion comprised of the flat base material and hook pieces itself from the sewing area or reducing the thickness of the flat base material in the sewing area of the hook portion, not only the sewing operation is made easier, but also affinity between the belt portion in the sewing portion and the second facing sheet material is improved, which is preferable. The effects which the present invention exerts are considerably great.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial perspective view of a core material for piping according to a first embodiment of the present invention as seen from the side of a hook piece;

FIG. 2 is a partial back side view showing the modified example of the cutout shape of the belt portion of the core material for piping of the present invention;

FIG. 3 is a partial back side view showing another modified example of the cutout shape;

FIG. 4 is a partial back side view showing further another modified example of the cutout shape;

FIG. 5 is an explanatory view showing a concept for assembling a seat cover obtained by sewing the core material for piping of the present invention to a seat pad of a passenger seat and the like;

FIG. 6 is an enlarged sectional view schematically showing the structure of major portions of the passenger seat and the like to which the seat cover is assembled;

FIG. 7 is a lamination exploded view schematically showing the configuration of a facing sheet material which is a component of the seat cover;

FIG. 8 is a partial perspective view of a core material for piping according to a second embodiment of the present invention as seen from the side of a hook piece;

FIG. 9 is a cross-sectional view of a core material for piping according to a third embodiment of the present invention; and

FIG. 10 is a cross-sectional view of a core material for piping according to a fourth embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, typical embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a partial sectional view of a core material for piping according to a first embodiment of the present invention. As shown in FIG. 1, a core material 10 for piping of this embodiment is comprised of a core material main body 13 and a hook portion 14. In the core material main body 13, a cord portion 11 having a substantially semi-circular section and a belt portion 12 having a substantially elongated rectangular section are integrally molded. The hook portion 14 is integrally molded by two-color molding on entire one surface in which the cord portion 11 and the belt portion 12 are continuous.

The entire single face of the core material main body 13 integrated with the hook portion 14 is formed as a same flat plane. The hook portion 14 is comprised of a flat base material 15 and a plurality of hook pieces 16 erected from the surface of the flat base material 15 on an opposite side to the core material main body 13. The belt portion 12 of the core material main body 13 and the hook portion 14 part integrated with the belt portion 12 are cut out in a zigzag shape having a mountain and valley. The core material 10 for piping having such a configuration is manufactured continuously by intermittently feeding a long core material main body 13 molded by extrusion preliminarily to a core material main body passage for lower mold (not shown) in an injection molding machine, and then integrally molding the flat base material 15 of the hook portion 14 and the hook pieces 16 on a single face thereof by injection molding in a continuous manner. According to this embodiment, the belt portion 12 and the hook portion 14 integrated with the belt portion 12 are cut out in a zigzag fashion, and the cutout shape is formed by punching out a portion corresponding to the belt portion 12 molded as described above. This punched-out shape improves the entire curving performance of the core material 10 for piping. Of course, the belt portion 12 may be formed in a usual long rectangular plane.

As for the zigzag-fashioned cutout shape, it can be formed in a zigzag shape along the curved line as shown in FIG. 1, and it can be also formed in a zigzag shape linearly, for example, as shown in FIGS. 2 to 4 so that in the engagement area of the belt portion 12 with the facing sheet material, the engagement area on the end portion side is as same as, or larger than that on the cord portion 11 side. In the FIG. 2, the cutout shape is formed to be a rectangle so that enough engagement strength with the facing sheet material is secured. The depth of the cutout at this time is preferably to be two thirds or more of the length of the belt portion 12 in the width direction thereof in order to secure the plasticity of the belt portion 12, and the width of this cutout is 5 mm or less, preferably is 2 to 5 mm. If the width of the cutout is more than 5 mm, respective portions of the belt portions 12 which are adjacent to each other so as to sandwich the cutout are too separated so that the engagement strength of the surface fastener is deteriorated. Further, when the interval of the belt portion 12 between the adjacent cutouts is formed to be 8 to 20 mm in the longitudinal direction of the core material 10 for piping, the plasticity is more increased and most appropriate flexibility can be obtained. In case the interval is less than 8 mm, the enough engagement strength of the surface fastener is hard to be obtained, and if the interval is more than 20 mm, the desired flexibility is hard to be obtained.

FIG. 3 shows that the cutout shape is so formed that the cutout width is gradually increased straightly toward the cord portion 11 side, and FIG. 4 shows that following the rectangular cutout, the top end portion thereof on the cord portion 11 side is cut out to be a circular form which has larger diameter than the dimension of the cutout width of the rectangular cutout. In this way, by setting the cutout area on the cord portion 11 side to be larger than the cutout area on the belt portion 12 side, the plasticity of the belt portion 12 is secured, and at the same time, the engagement area of the hook portion becomes wide so that engagement strength is increased.

An important point of this embodiment exists in that the material used for the core material main body 13 and the material used for the hook portion 14 are different from each other. According to this embodiment, the core material main body 13 is composed of polyolefin base elastomer resin, and the hook portion 14 is composed of polypropylene like conventionally. The softness of the polyester base elastomer resin is about 70 in durometer A to 60 in durometer D, which is harder than ordinary rubber, but it is much softer than ordinary thermoplastic synthetic resin and easy to be deformed. On the other hand, the hardness of polypropylene used in the hook portion is 80 to 100 in Rockwell hardness, and the hook portion can easily engage the seat cover, particularly, a facing layer 19 c. The bending elastic modulus of the same polypropylene is preferred to be 1500 Mpa, and has an appropriate hardness and bending elastic modulus. The thermoplastic elastomer resin is not limited to polyester base, but considering the affinity with the mating hook portion 14, various kinds of elastomer resins such as styrene-butadiene base, polyolefin base, polyvinyl chloride base, and polyamide base may be used.

FIG. 5 is a conceptual view when assembling a seat cover, on which the core material 10 for piping of this embodiment having the above-described configuration is sewed, to a seat pad of a passenger seat 17 and the like. FIG. 6 is a sectional view of a core material for piping providing portion of the passenger seat 17 and the like on which the seat cover is assembled.

In order to provide the core material 10 for piping made of synthetic resin of this embodiment along a ridge portion 17 a of a passenger seat 17 and the like shown in FIG. 6, firstly the core material 10 for piping is sewed to a predetermined position of the seat cover 18. The ridge portion of the passenger seat 17 and the like is not limited to simple linear one but is often curved as if it is twisted as shown in FIG. 5. For this reason, the core material 10 for piping is seldom sewed linearly to the seat cover 18 but often sewed to the seat cover 18 as if it is twisted with large and small curves.

This kind of the seat cover 18 has the core material 10 for piping and first and second facing sheet materials 19, 20. In a conventional facing sheet material, for example, fiber woven fabric, natural leather or synthetic leather is used as a facing layer, thin and soft urethane foam is used as its intermediate layer, and rough and thin warp knitted fabric using thin thread is disposed as back side base fabric and those are laminated and integrated by lamination processing. According to this embodiment, as shown in FIG. 7, the first and second facing sheet materials 19, 20 have facing layers 19 a, 20 a and intermediate layers 19 b, 20 b having the same material and structure as conventionally. However, a plurality of piles are formed positively on a face of the back side base fabric 19 c, 20 c to intensify an engagement ratio with the hook pieces 16. The pile fibers at this time are composed of a plurality of thin filaments. The first and second facing sheet materials 19, 20 may be composed of the same material and structure or may be composed of different materials and structures. Of course, the back side base fabric 19 c, 20 c is not limited to warp knitted fabric, but may be woven fabric.

When the seat cover 18 is manufactured by sewing the core material 10 for piping as shown in FIG. 6, the first and second facing sheet materials 19, 20 are overlapped so that their facing layers on the side edge portions of the sewed side are faced to each other in a conventional manner. In addition, the first and second facing sheet materials 19, 20 are sewed together with a first sewing thread 22 on a first sewing line along the boundary between the first and second facing sheet materials 19, 20 and the cord portion 11 and belt portion 12 of the core material 10 for piping. Also, the sewing is carried out while fixing up the surface on an opposite side to the hook portion 14 of the core material 10 for piping along the side edge portion curved as if the back side base fabric of the second facing sheet material 20 is twisted. Next, the first and second facing sheet materials 19, 20 are sewed together with a second sewing thread 23 along a second sewing line on the front edge of the cord portion 11 on an opposite side to the belt portion 12. After this sewing is finished, the second facing sheet material 20 is folded back so as to wrap the cord portion 11 of the core material 10 for piping. Then, the hook pieces 16 of the core material 10 for piping sewed along the side edge of the second facing sheet material 20 are engaged with the pile face inside of the folded back portion of the second facing sheet material 20, thereby finishing the seat cover 18.

When the core material 10 for piping is sewed to the first and second facing sheet materials 19, 20, in case of the core material for piping described in Japanese Patent Laid-Open Publication No. 2005-40158, a sewing needle is likely to be broken along the boundary between the cord portion and the belt portion because all the core materials are composed of synthetic resin materials such as polypropylene. According to the present invention, elastomer resin which is soft and easy to be deformed is used in the core material main body 13 in order to set the hardness of the core material main body 13 comprised of the cord portion 11 and the belt portion 12 lower than that of the hook portion 14, and ordinary synthetic resin such as polypropylene having a higher hardness is used for the hook portion 14. The flat base material 15 of the hook portion 14 is integrated with the core material main body 13 so as to intensify its strength. Also, as shown in FIGS. 1 and 6, even if the thickness of the flat base material 15 is reduced as much as possible, a necessary strength for the hook portion 14 is secured, and at the same time, piercing of the sewing needle is facilitated, so that no breaking of the sewing needle occurs.

As shown in FIGS. 5 and 6, the seat cover 18 completed in this way is assembled so as to cover the seat pad 21 such as the passenger seat like conventionally. The core material for piping described in Japanese Patent Laid-Open Publication No. 2005-40158 employs thermoplastic synthetic resin such as polypropylene having a high hardness at all the core materials at the time of this assembling. For this reason, the core material for piping disposed along the inside below the ridge portion 21 c projecting outwardly so as to be curved as if it is twisted backward between an arm resting portion 21 a and a side wall portion 21 b of the seat pad 21 is strongly repulsive, so that the core material for piping tries to restore to its linear state. In an area where the seat cover 18 sewed so as to conform to the shape of the ridge portion 21 c is especially twisted, it is likely that the seat cover 18 is flipped outward to provide a finishing not good to see different from a desired appearance of the seat pad.

Contrary to this, the core material 10 for piping of this embodiment uses elastomer resin having a plasticity and being deformed easily in its core material main body 13, and ordinary thermoplastic resin having a required hardness is used in the hook portion 14 in which a predetermined engagement strength is required. Accordingly, the core material 10 for piping is excellent entirely in its curving performance. When the seat cover 18 on which the core material 10 for piping is sewed is assembled so as to cover the seat pad 21 so as to conform to the shape of the ridge portion 21 c, it can be conformed easily to that shape, so that a step having a predetermined shape is obtained in the seat cover after the covering. As a consequence, a passenger seat 17 and the like excellent in its appearance can be obtained. Further, because the hook pieces 16 of the hook portion 14 have a required hardness and elasticity, the plurality of hook pieces 16 of the hook portion 14 engage piles on the back side of the second facing sheet material 20 securely. As a consequence, even if forces are applied to the passenger seat 17 and the like from various directions, the inner faces of the second facing sheet material 20 are never separated in the folded back portion of the second facing sheet material 20 embracing the core material 10 for piping, whereby the shape of the cord portion never being collapsed.

FIG. 8 is a partial perspective view of a core material for piping according to a second embodiment of the present invention. Same reference numerals are attached to components substantially coincident to the first embodiment, and description thereof is omitted. According to this embodiment, the flat base material 15 is not continuously molded at the molding of the hook portion 14, but part of the flat base material 15 is missed at a required interval in the longitudinal direction of the core material 10 for piping so as to expose part of a joint face between the hook portion 14 and the cord portion 11 and the belt portion 12 directly to outside and form a groove portion 10 a. By formation of this groove portion 10 a, the entire core material 10 for piping is easy to be curved.

FIG. 9 shows a cross-sectional view of a core material for piping according to a third embodiment of the present invention. In this embodiment, only portions substantially different from the first and second embodiments are described. Same reference numerals are attached to substantially the same components as the previous embodiments, and description thereof is omitted. According to the third embodiment, the flat base material 15 of the hook portion 14 of the above-described embodiments is removed, and the hook pieces 16 having a high hardness are erected directly from a one surface of the core material main body 13 having a plasticity and excellent curving property composed of elastomer resin. As a consequence, while the engagement strength of the hook pieces 16 is secured, the entire core material 10 for piping is formed to be more plastic and easier to be curved than that of the second embodiment.

FIG. 10 shows a fourth embodiment of the present invention. Same reference numerals are attached to components substantially coincident to the first to third embodiments, and description thereof is omitted. According to the fourth embodiment, the hook pieces 16 are removed from an area along the sewing line of the belt portion 12 of the core material 10 for piping, and a corresponding area of the belt portion 12 is partially removed. Other features are substantially as same as those of the first embodiment. Thus, same reference numerals are attached to coincident components between the respective embodiments. Because in this case, what is required is to construct a sewing area 10 b as thin as possible and remove an obstructive portion, it is permissible to leave the belt portion 12 and remove the flat base material 15. In this case, not only sewing operation is facilitated, but also breaking accident of the sewing needle is eliminated. 

1. A core material for piping comprising a cord portion and a belt portion which are molded from a synthetic resin material and having a hook portion integrally formed on one surface of at least any one of the cord portion and the belt portion, the core material for piping being provided to a required position of a facing sheet material of, such as a seat, wherein hardness of the hook portion is set higher than the hardness of the cord portion and the belt portion.
 2. The core material for piping according to claim 1, wherein the cord portion and the belt portion are composed of elastomer resin, and the hook portion is composed of thermoplastic resin.
 3. The core material for piping according to claim 1, wherein the hook portion is provided continuously or intermittently on entire one surface of at least any one of the cord portion and the belt portion.
 4. The core material for piping according to claim 3, wherein a surface of the core material for piping on which hook pieces are formed is a flat plane. 